Groton Town Police said they also the State Police Tactical Team, which received support from Rhode Island and Massachusetts State Police. The FBI and Naval Criminal Investigative Services (NCIS) were also called in.

Assistant Special Agent Robert Fuller of the New Haven office of the FBI said, "Our SWAT team and our crisis negotiation team came out early on, based on a request from Connecticut State Police and to assist Groton with the investigation."

The standoff continued overnight into the morning hours, draining manpower.

"Rhode Island and Massachusetts state police SWAT teams came down to assist with the relief efforts for our guys who had been out all night," said Trooper First-Class Tanya Compagnone of the Connecticut State Police.

The Tactical Team made numerous attempts to contact the suspect, and on Wednesday morning officers saw movement inside the home.

"There was one deceased party inside the residence," Groton Town Police Department Chief Luis Fusaro said. Police did not identify the deceased, but did say it was the husband of the woman who initially contacted police. They did not provide any probable cause of death at the scene; the Office of the State Medical Examiner will conduct an autopsy.

The case remains under investigation by Groton Town Police, with assistance from the state police. FOX61 will have details online as they become available and Tony Terzi will have a complete report live on the FOX61 News at 4 & 5 p.m.

A standoff, lasting over 17 hours, ended with the discovery of a deceased man inside of this #Groton residence, in a neighborhood that has traditionally been #Navy housing. No identity, but police confirm his wife said he fired his gun inside their house last night. @FOX61Newspic.twitter.com/gTCtWAPcny